


Sometimes a third wheel adds stability

by moonblossom



Category: Sherlock (TV)
Genre: Anal Sex, Banter, Fingering, Fluff, Humour, Johnlockary - Freeform, Multi, Pegging, Threesome, m/m/f
Language: English
Status: Completed
Published: 2014-01-04
Updated: 2014-01-04
Packaged: 2018-01-07 05:48:39
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,220
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1116257
Author URL: https://archiveofourown.org/users/moonblossom/pseuds/moonblossom
Summary: <blockquote class="userstuff">
              <p>Mary learns that John has never penetrated Sherlock and sets out to repair that oversight.</p>
            </blockquote>





	Sometimes a third wheel adds stability

**Author's Note:**

> Unabashed John/Mary/Sherlock smut. I make no apologies.
> 
> Don't worry, John/Sherlock shippers - I am not giving up my OTP to end all the OTPs. I'm just going to be doing some occasional inclusion of Mary in one way or another, sometimes as part of a triad, sometimes as a friend to both of them.

"What do you mean you've never fucked Sherlock?" Mary cocks her head, grinning at John in a way that makes him tingle all the way down to his fingertips. "Is he not into that?" She's perched in Sherlock's chair, bare feet with orange toenails wriggling into the faded rug. Sherlock's staring out the window behind her, also barefoot. John wonders vaguely if he should take his socks off too, if there's some sort of breach of etiquette going on here.

John stares at some vague spot over Mary's left shoulder, only to have that spot suddenly filled with six feet of unfairly handsome consulting detective. Sherlock smirks and leans over, purring into Mary's ear as he perches on the arm of his own chair.

"You've slept with him, haven't you?"

Mary leans back, rather intentionally rubbing her cheek against Sherlock's. John fidgets in his chair; watching the two people he loves most in the world like this feels almost inappropriate.

"'Course I have, you silly man. I thought you weren't one for rhetorical questions." John grins at her response. There's something immensely satisfying about someone other than himself calling Sherlock out on his nonsense.

"Then you are... intimately familiar with the dimensions of his..." Sherlock pauses, lips brushing against the tiny pink shell of Mary's ear. "Cock."

Realisation dawns on Mary's expressive face and John's not sure whether he should feel boastful or mortified.

"It is rather girthy. But you've done... other things, yeah?" Her voice is hushed and girlish, a blatant mockery. A grown woman playing innocent. John groans. He's really got no hope against these two when they set their mind to filthy things.

"Yes, thank you, Mary. Our sex life was plenty fulfilling before you came along." John sinks down into his chair, wondering if he should just leave the two of them alone for a bit.

"Yes, Mary. Your husband is a very inventive and attentive lover. As you are no doubt aware. There is more to life than penetrative sex."

Mary, bless her, reaches around and pinches Sherlock's arse. John's cock twitches slightly at the sight. He's not hard, not yet, but if this conversation goes on much longer that's going to change soon.

"Of course there is. And he is quite a crafty little man."

"Oi, I'll thank you not to call me little." John huffs, but he's not irritated. Not really.

Sherlock and Mary turn to each other in alarming synchronicity and grin. "Not where it counts, anyway," she trills, and Sherlock presses an unexpectedly sweet kiss to her forehead. "But really, do you _want_ it?"

John's not entirely sure who she's asking. Does he want to fuck Sherlock? Of course he bloody does. He's just got no idea if Sherlock wants it. Things before Mary came along were always more than satisfying. Oral, manual, Sherlock fucking John, one particularly memorable instance of rutting against each other on Mycroft's desk...

"Yes." Sherlock's voice is throaty and ragged, bringing John back to the present. "I do. I've just never..." There's a tremulous quaver to his words, he's playing the innocent virgin, but under that John can tell that he's telling the truth.

Mary's face lights up like it's Christmas, and there's a flood of... _something_ through John's body. Panic. Arousal. Both. They're up to something, and he's going to end up in the middle again. She gives Sherlock's arse one last squeeze and John does his best not to feel jealous or left out.

"Go on then. Sherlock's room. Consider it an experiment. Sherlock, be naked when I get there. John, also be naked, or maybe just your pants. I don't need you yet. I just like looking at you." She hoists herself out of the chair, her slight figure dwarfed by the deep dark leather, and very nearly skips up the stairs to the upstairs bedroom. John groans and scrubs his face with his hands.

When he looks up, Sherlock is looming in front of him, the outline of his cock, already starting to harden, visible in his trousers. He holds his hands out to John who accepts them gratefully. It's not as if the three of them falling into bed together is a new development, but the idea of Mary somehow facilitating him _fucking Sherlock_ is novel and exciting.

John's got no idea what her plans are, but he's more than eager to find out. He follows Sherlock into the bedroom, sparing a moment to reach out and gently stroke the spot on his arse Mary had pinched earlier. Sherlock makes a muffled noise of contentment as he begins undoing his shirt. He strips down efficiently and John takes a moment to admire the view before waffling a bit and trying to decide if he should undress too.

In the end, John settles for stripping down to his vest and pants, thankful he wore a tidy enough pair. Clean, black, no holes. They've both seen him in far worse, but there's a heady whiff of anticipation in the air and he feels as though he should be dressed up for the occasion.

Sherlock, either out of some strange willingness to oblige Mary or out of sheer selfish laziness, has sprawled across the entire bed, his cock thick and heavy with anticipation. John perches on the edge of the bed, one hand absently stroking Sherlock's long, inviting thigh. Sherlock reaches up and places one hand soothingly on the small of John's back, thumb just running under the edge of his pants.

John is debating curling up next to Sherlock and snogging him senseless when Mary's familiar little footsteps echo out in the corridor. John leans forward slightly, body alight with anticipation. Sherlock, to the casual observer, would seem almost disinterested, but John can read his face. He's eager, alert, curious, excited by the prospect of something new. It's clear he's got no idea what Mary's up to either.

What exactly Mary is up to becomes immediately evident when she struts into the bedroom. There's really no other word for the way she's walking, either. She should have her own theme music. She's wearing one of John's ratty old cotton crew-necks, loose and faded and hanging off one shoulder. Her pert little breasts are distending the front, nipples hard and slightly visible through the thin fabric. John's thumbs twitch with the urge to reach out and stroke them. The bottom of the shirt is rucked up, caught on the bright purple silicone cock jutting out of the harness she's got strapped around her hips. It even looks like a girlish pair of panties - reinforced cotton, pink with ruffles across the bum. She really is playing up the innocent virginal thing. _Christ_.

There's a loud ringing in John's ears, the furious pounding of his heart as his cock goes from mildly interested to rock-fucking-hard in a timeframe that he hasn't experienced since he was a teenager.

Sherlock's reaction is equally alarming. His eyes are alert and sparkling, pupils dark and wide. There's a delicious flush across his cheeks and down his throat, and as John's eyes trail down his body, they take in Sherlock's cock, also now hard and eager. Impulsively, he reaches out and strokes two fingers down the length, and Sherlock gasps.

"Ohhhh. She is clever! It's a reasonable size, good for a stretch..."

"Glad you've caught on then." Mary smirks and pulls John's shirt over her head, exposing the soft, gentle curves of her body, so in contrast to the sharp planes and angles that compose Sherlock. For a moment, John just marvels at his luck.

She steps forward, parting John's legs with her knee and positioning herself between them. John leans forward, eagerly taking one of her tight, dark nipples into his mouth and rolling his tongue around it. She moans quietly before gently but forcefully turning his head to the side.

"Not yet, darling. We've got Sherlock to take care of."

John's heart pounds erratically, and he's more than a little concerned he's going to die of cardiac arrest before the evening is out. Mary strokes his cheek, calming him slightly, and Sherlock chuckles behind him.

"Lie down, love, next to Sherlock. Sherlock, if you need anything, if you get overwhelmed, speak up. John's right there for you."

Unable to disobey an order from either of them, John curls up on the bed next to Sherlock. He places one hand on Sherlock's abdomen, palm rubbing over the thin trail of coarse hairs he finds there. Sherlock gasps slightly, raising his hips up off the mattress, desperate for more contact. Mary settles down on her knees at the end of the bed and Sherlock plants one foot on either side of her, spreading his legs in clear invitation.

"Now, do you boys have any lube?" Her voice is a teasing rumble again; because of course they fucking have lube. John fumbles for it in the nightstand and tosses the bottle towards the foot of the bed before reaching up to cup Sherlock's cheek, to turn his head and kiss him fiercely. Sherlock's mouth is hot and dry as John's tongue slips in. He presses his own erection against Sherlock's hip, the rough texture of his pants adding a delicious layer of friction.

Sherlock gasps into John's mouth, and John breaks the kiss to look up. Mary's staring down at Sherlock intently, a look of rapt concentration on her face as she slips two fingers into Sherlock's hole. Her hands are tiny, her digits clever and precise. John knows from experience, and he grins, heart fluttering as he watches the expressions floating across Sherlock's face as he feels Mary's fingers inside of him for the first time.

Gently, John takes Sherlock's cock in hand, stroking him slowly. He's not trying to accomplish anything specific, not yet, just trying to ease Sherlock into all of this, to add another layer to the experience. Sherlock huffs, rocking his pelvis back and forth. John's still pressed against Sherlock hips and he groans quietly as Sherlock's movements increase the friction on his own erection.

There's a sharp gasp, Sherlock tosses his head wildly against the pillows and John knows Mary's found his prostate. She can be a complete and utter tease, totally merciless, but she's taking it easy on Sherlock, who already looks close to being completely overwhelmed.

Unable to help himself, John sits up to get a better look, and for a moment he nearly wishes he hadn't, because fuck that's a beautiful picture. Sherlock's eyes are closed in concentration, his lower lip swollen and red where he's been chewing on it. Mary's got a calm, nearly beatific expression on her face and three fingers deep inside of Sherlock. John's prick throbs, full and heavy, trapped inside his pants. Groaning, he slips them down and relieves the pressure slightly.

"Soon, love." Mary turns to look at him and winks, and Sherlock gasps again. She pulls her hand out, letting John watch as Sherlock's arsehole twitches and closes slowly, so slowly. Mary shifts her weight and slathers up the strap-on with lube. There's something impossibly hot about watching her to that, and John grips the base of his cock again, trying to calm himself. He strips down properly, fumbling as he pulls his vest over his head, not wanting to miss a single moment.

"Pass me a pillow, would you?" It seems like John's life is a series of orders to fetch things lately, but this is one he's more than eager to oblige. He tosses the pillow not currently trapped under Sherlock's head down to Mary, who deftly slips it up under Sherlock's hips. John leans forward and gives Sherlock's cock a few quick strokes that make him gasp before settling back to watch Mary slide in. She's got the head of the toy pressed lightly against Sherlock's hole, good and loose now, and she's making the most minute little rolling motions with her hips.

Sherlock's lips are parted slightly, he's nearly panting with eager anticipation. John reaches out and takes Sherlock's hand, lacing their fingers together and squeezing encouragingly. As he does so, Mary slides in slowly. Sherlock lets out one long, low, guttural groan as Mary slides home. Smoothly, one solid thrust, but so slow. John's hand aches slightly as Sherlock squeezes harder, but neither of them are ready to let go.

"Not..." he gasps out, between ragged breaths. "Not too long, Mary. I want him." Sherlock's raw vulnerability makes something shatter inside of John's chest, right between his lungs. Mary, perfectly understanding creature that she is, merely nods. She leans forward, one arm braced on the bed and the other stroking John's hip, and spreads her knees slightly. The movement causes Sherlock's legs to part further and he moans again.

"Raise your legs up, love. Put one on my shoulder if it helps." She murmurs, gentle and competent all at once.

"She's sturdier than she looks. Go on." John blurts out, before he realises what he's saying. Thankfully Mary just turns to him and grins before returning all her attention to Sherlock. She thrusts her hips steadily, increasing the pace slightly, and it's not long before Sherlock is rocking back, meeting her thrusts in equal measure. The sight of the two most important people in John's life fucking each other with passion and abandon is lighting a fire in John's belly, and he starts absently stroking himself, his hand roaming over his thighs, his cock, his balls. He's adamant he can hold out until it's time.

"John..." Mary's voice is pleading and breathy, starting to roughen around the edges. "Come sit behind me."

More than willing, John lets go of himself and shifts, clambering awkwardly across the bed and sitting behind her. Between thrusts, she manages to reposition herself so she's nearly sitting in John's lap, the ruffles over her pert, round arse rubbing deliciously against his cock every time she thrusts into Sherlock. John uses the position as an opportunity to get his hands on Mary. He brings his hands around and cups her breasts, two perfect, warm little handfuls, and runs his thumbs over her nipples.

He feels her gasping against him, feels her head falling back against his shoulder. His cock twitches, aching and eager, sliding easily against the ruffled fabric back of the harness. It seems to spur Mary further, and she starts thrusting rapidly into Sherlock, sliding the toy nearly completely out of him with each stroke. John peers over her shoulder, the view giving him an inkling of what he's in for soon, increasing the anticipation ten-fold. He's hypnotised by the sight of the thick purple shaft sliding deeply into Sherlock.

"Christ, stop. Ma... pl..." Sherlock is trembling, reaching out to stroke whatever knee he can find. "Stop... John. I want John. I'm ready."

Mary gives a little wiggle, rubbing herself against John's erection and slipping the dildo out of Sherlock all in one smooth movement. John gasps, pinching her nipples gently and she sighs contentedly.

"Sherlock?" She asks, calm and soft and blurry around the edges.

"Mmf?"

"I am going to move out of the way, and John is going to take over. Is that alright?"

Suddenly, the Sherlock they know and love is back with a vengeance. He sits up and rolls his eyes. "I am quite certain that is exactly what I asked for. Mary, you are wonderful, but you are not my John."

John doesn't even try to disguise the smug grin that crosses his face. It stays there until Mary playfully elbows him in the ribs as she clambers over Sherlock, the dildo in the harness bouncing and bobbing like some obscene purple buoy at high tide.

Muscles somehow tense and trembling all at once, John shuffles forward on his knees. He takes a moment to appreciate the sight laid out before him, Sherlock panting and flushed with arousal, Mary stripping out of the harness and kneeling next to Sherlock's face. His cock throbs and twitches eagerly, and he takes it in hand, brushing the glans over Sherlock's loose pink arsehole without exerting any pressure. Sherlock whimpers and moans encouragingly.

"Mary, would you do the honours?" John smirks, holding the lube bottle up.

Still playing the coquette, Mary pretends to look scandalised but she shuffles over anyway. She makes such a show of slathering her hand with lube that John has to bite his cheek. Mary wraps one little hand tightly around his aching prick and strokes languorously, swirling her fingers around the head and spreading the slick fluid around, a mess of lube and pre-come. John groans, utterly distracted, until he remembers he has to hold on. He cups her jaw with one hand and kisses her quickly.

"Please, stop. Or this will all be over too quickly."

Sherlock raises his head off the pillow again to glare at them briefly before falling back down with a thud that speaks volumes. Impatiently, he cants his hips upwards and throws one leg over John's good shoulder. John whimpers as Mary sweeps two fingers around Sherlock's hole, making sure he's good and slick. These two will be the death of him.

John leans forward, bending Sherlock's leg between them, tilting until he can reach Sherlock's mouth. He kisses Sherlock again, eager and sloppy and beautiful. Sherlock feels nearly feverish beneath him, but then John suspects he's more than a bit overheated himself. He coils his tongue around Sherlock's and lines the head of his cock up. He stills his hips and pulls back, sucking hard on Sherlock's swollen lower lip.

"Ready?"

Rather than answer like a proper human being, Sherlock just grunts and angles his hips, thrusting them forward. John bites back a hiss and gives in, gripping himself tightly and guiding the head of his cock into Sherlock. It's warm and slick and perfectly snug, even after Mary's stretching. As he slides in, a fraction of an inch at a time, he buries his face in Sherlock's throat. He can smell Sherlock, sweat and salt and that familiar tang, and he can smell Mary, kneeling so close. Warm and comforting and earthy, heady with her own arousal.

John closes his eyes, thrusting his hips minutely, pushing himself deeper into Sherlock, revelling in the act that's bringing all three of them closer together. He can feel Sherlock's breath, fast and shallow, feel Mary's hand stroking soothingly down his own spine. Her other hand is buried between her legs; the slick wet sound of her fingers fucking her own cunt is like a shot of adrenaline straight to John's heart.

Unable to hold back any longer, he slides the rest of the way in, groaning as Sherlock's ring of muscle stretches and twitches to accommodate his girth.

"Fuck, Sherlock... God..."

"Yes. Ugh, yes," is all Sherlock manages to spit out in reply. He twists sharply, wriggling and relaxing around as John buries himself to the root. Sherlock wraps both legs around John's waist, locking them together. John does his best to hold still, to give Sherlock a moment to acclimatise himself to the thickness inside of him.

As he tries to calm his breathing, Sherlock turns and it's as if he's noticing Mary anew. His eyes are wide as he stares, transfixed, by her hand. Teasingly, John pulls out halfway and slips back in, thankfully encountering no resistance. Sherlock glances at John briefly, his eyes wide and uncertain, before turning back to Mary.

"Allow me."

John's heart thumps in his chest, a sudden rush of blood making his cock even harder. Usually, he is the thread connecting Sherlock and Mary. They're terribly fond of each other, but Sherlock's never been particularly keen on being sexually intimate with a woman. Then again, Sherlock had never been particularly keen on being sexually intimate with _anyone_ , far as John knows. The fact that he's offering speaks volumes, and if the look on Mary's face is anything to go by, she's a little overcome by it all.

She spreads her legs theatrically, in invitation. John turns his head, looks away, because if he watches too intently this is all going to be over before it's properly begun. He closes his eyes, lets his head fall forward, and thrusts slowly. Sherlock's moans are wholly encouraging, deep and enthusiastic, punctuated by Mary's sharp, mewling cries and the soft wet sounds of Sherlock's fingers buried deep inside of her.

With a deep groan, John begins pistoning his hips in earnest. He can't help it, he opens his eyes and marvels at the sight of his cock stretching Sherlock to his limit, sliding smoothly in and out of hip as their hips rock up to meet each other. He steals a glimpse of Mary, writhing eagerly on Sherlock's hand, her breasts bouncing enticingly. She's gripping the headboard with one hand for support, the other braced against Sherlock's chest.

John grips Sherlock's hips, pulling them tighter together. The pressure that's been simmering slowly in his abdomen since this started is building, the tight heat of Sherlock's arse coaxing out what will undoubtedly be a massive orgasm.

There's a sharp uptick in the pitch and frequency of Mary's moaning, abrupt little gasping moans, and John knows from experience that Sherlock's found her clit. Sherlock looks up at John, wide eyed and glassy and desperate, and John nods. He increases the speed of his thrusts, and he can tell that Sherlock's mirroring the pace. Within moments, Mary's screaming, head thrown back, her whole body an arc of deliciously sensuous curves as the orgasm hits her. John stills, Sherlock stills, and she rides it out, rubbing her cunt furiously against Sherlock's long, smooth fingers.

One final shudder and then her body relaxes and she sucks in a mouthful of air, gasping heavily. John's fingers are undoubtedly gripping Sherlock's hips to the point of discomfort, but he's not saying anything. Mary falls to the mattress in a giggling heap, stretching out languidly beside Sherlock. She glances up at John, eyes glazed and cheeks flushed.

"I can see why you've been holding onto him. Damn." She reaches up and kisses Sherlock's cheek, and he whimpers.

John sucks in a deep breath and starts rocking his hips again. As he does so, he looks down at Sherlock's cock, deep purple and leaking at the head. Taking pity, he wraps one hand tightly around the shaft. Mary, clever as she is, reaches down and wraps her own hand around it as well, lacing her fingers with John's. He gives her hand a tight squeeze, constricting Sherlock's erection as he does, and Sherlock gasps sharply.

Sherlock reaches up, dragging two slick fingers across John's cheek and over his lips. Hungrily, John sucks them into his mouth, savouring the feel of those long clever fingers, the taste of Mary's cunt all over them. The combination is too much for John to handle, and he loses whatever finesse and control he may have had, pistoning furiously into Sherlock. He does his best to stroke Sherlock's cock in time with his thrusts, but he is erratic and distracted. Thankfully Mary is helping. Between their hands, Sherlock is rock under velvet, the soft skin sliding smoothly up and down his length.

John feels his thighs trembling, feels Mary's other hand stroking his hip encouragingly, and he is lost. He buries himself deeply inside of Sherlock, hears Sherlock moaning loudly, so loudly, and bites back one sharp cry of his own as he climaxes, wave after wave of dizzying whiteness hitting him. He feels Sherlock tightening further around him, hips rising up off the mattress as Mary continues to pump her hand, feels Sherlock spilling liquid heat out over both their hands, and then John collapses.

When he finally gains control of himself, it's hard to tell which limbs belong to whom, tangled up and sweaty as they all are, but John has no inclination to move just yet. John has somehow fallen between them; Mary's nuzzling her face sleepily into the curve of his throat, and Sherlock's hand is thrown possessively across his chest.

"John." Sherlock's voice is faint and gritty. All that panting earlier must have dried his throat out. John makes a mental note to get them all some water as soon as his legs feel a bit less like jelly. "John, you have been holding out on me."

John flushes. He's a good lover, he knows he is, but it's still good for the ego to hear it now and again.

"Thank you, Sherlock. I enjoyed myself too."

"What? Oh, yes, the sex. That was lovely also." Sherlock raises his hand off John's chest to flap it dismissively in mid-air as he's speaking. "But no, I was referring to Mary. I knew she was clever, but I'd like to amend that. She's a proper genius."

"Aw, Sherlock. You're too sweet." John's eyes are closed, but he's fairly certain he can _hear_ Mary rolling her eyes as she's talking. Good lord. How did he end up with two of them? He'd be offended, but Sherlock's got a point.

"Really, I have no idea why neither of us ever thought of building up to it with something like that," Sherlock mumbles, incredulous of his own lack of insight.

Mary lets out a contented purr, rolling onto her back. "It's because you're both idiots."


End file.
